Messages in this thread | | | Date | Tue, 6 Oct 2015 14:03:48 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 07/13] rcu: Move preemption disabling out of __srcu_read_lock() |
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On Tue, Oct 06, 2015 at 10:32:24PM +0200, Peter Zijlstra wrote: > On Tue, Oct 06, 2015 at 01:19:15PM -0700, Paul E. McKenney wrote: > > On Tue, Oct 06, 2015 at 10:07:25PM +0200, Peter Zijlstra wrote: > > > On Tue, Oct 06, 2015 at 09:13:42AM -0700, Paul E. McKenney wrote: > > > > Currently, __srcu_read_lock() cannot be invoked from restricted > > > > environments because it contains calls to preempt_disable() and > > > > preempt_enable(), both of which can invoke lockdep, which is a bad > > > > idea in some restricted execution modes. This commit therefore moves > > > > the preempt_disable() and preempt_enable() from __srcu_read_lock() > > > > to srcu_read_lock(). It also inserts the preempt_disable() and > > > > preempt_enable() around the call to __srcu_read_lock() in do_exit(). > > > > > > Did you not simply want to use: preempt_disable_notrace() ? > > > > I believe that tracing the preempt_disable() in srcu_read_lock() and > > srcu_read_unlock() is actually a good thing. Or am I missing your > > point? > > Depends a bit on why we needed this change in the first place -- which, > going by the other branch of this thread, seems lost. However, > preempt_{dis,en}able_notrace() will not end up in any tracer/lockdep and > generate the minimum code that preserves the required semantics.
True enough! But can all architectures locate the TIF in all contexts?
Thanx, Paul
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